O Pioneers! from 1913 was written by Willa Cather while she was living in New York. It was her second published novel. The title is a reference to a poem by Walt Whitman entitled "Pioneers! O Pioneers!" from Leaves of Grass (1855).
The book tells the story of the Bergsons, a family of Swedish-American immigrants living near a town (fictional) called Hanover, Nebraska, in in the farm country around the turn of the 20th century. Alexandra Bergson, the main character, inherits the family farmland when her father dies, and she dedicates her life to making the farm viable at a point in time when many other immigrant families give up and leave the prairie. The novel is also deals with two romantic relationships, one between Alexandra and family friend Carl Linstrum and the other between Alexandra's brother Emil and the married Marie Shabata.
The book is divided into five parts, each of which has numerous chapters.